The present invention relates to a treatment accessory for an endoscope, especially to a treatment accessory which is used to excise and/or collect material from inside a human body, such as a polyp or the like.
As the treatment accessory of the above type, a grasping accessory is well known. The grasping accessory is provided with a cover tube, an operation wire slidably inserted through the cover tube, and a grasping unit (i.e., grasping forceps) connected at a distal end of the operation wire. The grasping unit is formed of, for example, a pair of wire members having predetermined resilience. The pair of wires neutrally open, and when the wire is pulled with respect to the cover tube so that a portion of the grasping unit is drawn inside the cover tube, the pair of wire members are closed as pushed by the end portion of the cover tube.
When material inside a human body is collected, the grasping accessory is inserted in an instrument channel of the endoscope, and the distal end portion of the grasping accessory is extended from a distal end of the insertion tube of the endoscope, which is inserted in the human body. The grasping unit is further extended from the distal end of the cover tube so that the pair of grasping members open. The grasping unit is then located at a position at which material, such as human tissue or the like is collected, and the operation wire is drawn inside the cover tube in order to close the grasping unit. In this situation, since the grasping unit is to be moved before the pair of grasping wire members are closed, the material may not be collected as intended, or collection may fail.
In order to overcome the above problem, Japanese Utility Model Publication No. HEI-2-39445 proposes a grasping accessory having a double tube structure. In the publication, a manipulation wire is enclosed by an flexible inner tube which is then enclosed by a coaxial flexible outer tube. The grasping accessory also includes a manipulation unit and an openable and closable grasping unit as described above. The grasping accessory operates such that the outer tube is fixed in position with respect to the instrument channel by a clamp member, or the like. The operation of the manipulation unit causes the inner tube to move and close the grasping unit while the grasping unit remains in a fixed position with respect to the axial direction.
However, in the material collecting accessory disclosed in Japanese Utility Model Publication No. HEI-2-39445, the manipulation unit is designed such that the operation to close the instrument is performed by an operator opening a hand (i.e., separating the thumb and fingers). With such an arrangement, it is difficult to apply sufficient force and is difficult to perform fine or urgent manipulation since the opening/closing movement of the hand is opposite to the opening/closing movement of the instrument.
Further, since the inner and outer tubes and the manipulation wire are all coaxial and connected to the manipulation unit, it is difficult to wash and disinfect the material collecting accessory.